Increased printing speeds are continually sought by users of printers, and there is therefore an ongoing desire by printer manufacturers to provide increased printing speeds. This is addressed in many ways, including improvements in software and firmware, improvements to the printing elements themselves (such as the speeds attainable by inkjet printheads) and improvements in the speed at which the moving parts of the printer can reliably move while maintaining the necessary accuracy of the printheads relative to the print medium.
The Hewlett Packard DesignJet 5000 is an example of a typical high quality inkjet printer. Inside the print body a scan axis comprising a track is mounted, and a print carriage scans along the track between incremental paper (or other print medium) advances. The print carriage has three bushings mounted on rails of the track, and a drive mechanism causes the carriage to be traversed back and forth while firmware within the printer converts received image files to swaths of halftone pixels in six colours. The firmware converts these halftone swaths to firing instructions for individual nozzles in a set of six printheads each provided on a print cartridge held on the carriage.
In high quality print modes, the swath is laid down in overlapping multiple passes. One of the reasons for employing higher numbers of passes is that in an eight pass print mode, for example, each pass lays down approximately ⅛th of the ink in a given area and thus each droplet laid down has an opportunity to dry before the next adjoining or overlapping droplet reaches the print medium. There is however a trade-off in that the printing speed of an eight-pass print mode is approximately eight times less than a single pass mode to achieve better print quality.
A further problem which arises in printing high quality textiles for example, is that a conventional CcMmYK set of six inks (comprising cyan, light cyan, magenta, light magenta, yellow and black) may not give sufficient colour fidelity. While one solution is to add additional ink colour cartridges to the print carriage, this results in a carriage which is larger than before. The scan axis or chassis along which the carriage travels will not be truly straight, and as a carriage travels along a non-linear scan axis, the increased length of the carriage will lead to greater errors in positioning droplets from different pens on the carriage.
It would therefore be desirable to provide a scan axis assembly which enables increased printing speeds to be attained. It also aims to provide improved printers and methods of manufacture of printers and their constituent parts.